/*
 * Copyright (C) The Apache Software Foundation. All rights reserved.
 *
 * This software is published under the terms of the Apache Software
 * License version 1.1, a copy of which has been included with this
 * distribution in the LICENSE.txt file.  */

package com.trs.infra.util;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;

import org.apache.log4j.helpers.LogLog;

// import java.awt.Image;
// import java.awt.Toolkit;

/**
 * Load resources (or images) from various sources.
 * 
 * @author Ceki G&uuml;lc&uuml;
 */

public class Loader {
    private static org.apache.log4j.Logger logger = org.apache.log4j.Logger
            .getLogger(Loader.class);

    static final String TSTR = "Caught Exception while in Loader.getResource. This may be innocuous.";

    // We conservatively assume that we are running under Java 1.x
    static private boolean java1 = true;

    static private boolean ignoreTCL = false;

    static {
        String prop = OptionConverter.getSystemProperty("java.version", null);

        if (prop != null) {
            int i = prop.indexOf('.');
            if (i != -1) {
                if (prop.charAt(i + 1) != '1')
                    java1 = false;
            }
        }
        String ignoreTCLProp = OptionConverter.getSystemProperty(
                "log4j.ignoreTCL", null);
        if (ignoreTCLProp != null) {
            ignoreTCL = OptionConverter.toBoolean(ignoreTCLProp, true);
        }
    }

    /**
     * This method will search for <code>resource</code> in different places.
     * The rearch order is as follows:
     * 
     * <ol>
     * 
     * <p>
     * <li>Search for <code>resource</code> using the thread context class
     * loader under Java2. If that fails, search for <code>resource</code>
     * using the class loader that loaded this class (<code>Loader</code>).
     * Under JDK 1.1, only the the class loader that loaded this class (<code>Loader</code>)
     * is used.
     * 
     * <p>
     * <li>Try one last time with
     * <code>ClassLoader.getSystemResource(resource)</code>, that is is using
     * the system class loader in JDK 1.2 and virtual machine's built-in class
     * loader in JDK 1.1.
     * 
     * </ol>
     */
    static public URL getResource(String resource) {
        ClassLoader classLoader = null;
        URL url = null;

        try {
            if (!java1) {
                classLoader = getTCL();
                if (classLoader != null) {
                    logger.debug("Trying to find [" + resource
                            + "] using context classloader " + classLoader
                            + ".");
                    url = classLoader.getResource(resource);
                    if (url != null) {
                        return url;
                    }
                }
            }

            // We could not find resource. Ler us now try with the
            // classloader that loaded this class.
            classLoader = Loader.class.getClassLoader();
            if (classLoader != null) {
                LogLog.debug("Trying to find [" + resource + "] using "
                        + classLoader + " class loader.");
                url = classLoader.getResource(resource);
                if (url != null) {
                    return url;
                }
            }
        } catch (Throwable t) {
            LogLog.warn(TSTR, t);
        }

        // Last ditch attempt: get the resource from the class path. It
        // may be the case that clazz was loaded by the Extentsion class
        // loader which the parent of the system class loader. Hence the
        // code below.
        LogLog.debug("Trying to find [" + resource
                + "] using ClassLoader.getSystemResource().");
        return ClassLoader.getSystemResource(resource);
    }

    /**
     * Are we running under JDK 1.x?
     */
    public static boolean isJava1() {
        return java1;
    }

    /**
     * Get the Thread Context Loader which is a JDK 1.2 feature. If we are
     * running under JDK 1.1 or anything else goes wrong the method returns
     * <code>null<code>.
     *
     */
    private static ClassLoader getTCL() throws IllegalAccessException,
            InvocationTargetException {

        // Are we running on a JDK 1.2 or later system?
        Method method = null;
        try {
            method = Thread.class.getMethod("getContextClassLoader", null);
        } catch (NoSuchMethodException e) {
            // We are running on JDK 1.1
            return null;
        }

        return (ClassLoader) method.invoke(Thread.currentThread(), null);
    }

    /**
     * If running under JDK 1.2 load the specified class using the
     * <code>Thread</code> <code>contextClassLoader</code> if that fails try
     * Class.forname. Under JDK 1.1 only Class.forName is used.
     * 
     */
    static public Class loadClass(String clazz) throws ClassNotFoundException {
        // Just call Class.forName(clazz) if we are running under JDK 1.1
        // or if we are instructed to ignore the TCL.
        if (java1 || ignoreTCL) {
            return Class.forName(clazz);
        }
        try {
            return getTCL().loadClass(clazz);
        } catch (Throwable e) {
            // we reached here because tcl was null or because of a
            // security exception, or because clazz could not be loaded...
            // In any case we now try one more time
            return Class.forName(clazz);
        }

    }
}
